The Mac Steam release list is a bit thin in terms of quantity this week, but the additions are pretty substantial. As promised, Half-Life 2 is now available for Mac and -- as we dearly, dearly hoped -- Episode Oneand Episode Two are also available. All three Half-Life 2 games feature cross-platform Steam Cloud support, meaning that players' games are saved on Steam's servers and can be opened from any computer, PC or Mac.

Additionally, Half-Life 2 and Episode One have been updated with over 40 new achievements. All three titles are currently 30 percent off: HL2 for 7 bucks; and Eps. 1 & 2 for $5.59 apiece. The complete Orange Box collection (with cross-platform Steam Cloud support across all games) is also currently discounted ($21), with the Team Fortress 2 for Mac release promised soon.

Finally, EVE Online: Tyrannis will launch for both PC and Mac later today, making it Steam's first game to launch simultaneously on both platforms.